(i) Field of the Invention:
This invention relates to a process for producing tricyclo[5.2.1.0.sup.2,6 ]decane-2-carboxylic acid which belongs to tricyclo carboxylic acids.
(ii) Description of the Prior Art:
Tricyclo[5.2.1.0.sup.2,6 ]decane-2-carboxylic acid is a known compound (refer to H. Koch et al, Liebigs Ann. Chem., 638, 111 (1960)), and it has been reported that ester derivatives and alcohol derivatives derived therefrom are very much useful as perfumes (refer to Japanese Patent Application Laid-Open No. 128735/1981).
Heretofore, the tricyclo[5.2.1.0.sup.2,6 ]decane-2 -carboxylic acid (I) has been produced by reacting 8-hydroxytricyclo[5.2.1.0.sup.2,6 ]decane (III) with carbon monoxide and water, or with formic acid in the presence of sulfuric acid to carboxylate the 2-position thereof. ##STR2##
Such a carboxylating reaction is generally referred to as Koch reactions, among which a method of reacting an alcohol or olefin with carbon monoxide and water in the presence of an inorganic strongly acidic catalyst is referred to as the CO pressure method, and a method of reacting formic acid is referred to as the formic acid method.
However, these known Koch reactions are not completely satisfactory as the process for producing tricyclo[5.2.1.0.sup.2,6 ]decane-2-carboxylic acid since they have the following defects. Specifically, the CO pressure method involves drawbacks in that (1) since it is important to increase the pressure of carbon monoxide (CO) for suppressing the formation of tars in order to improve the yield, it is required to use a pressure-proof vessel, which means a restriction in view of the facility; (2) it requires energy for pressurizing the carbon monoxide; and (3) since the reaction is carried out in the presence of a water-containing acid catalyst, special materials are required for the autoclave, which causes an increase in the installation cost. The formic acid method, although being free from the drawbacks as in the CO pressure method since the reaction can be taken place under ambient pressure, involves several drawbacks in that (1) the yield will be decreased unless formic acid is used in a large excess to the alcohol or olefin; (2) the excess formic acid in the reaction system is decomposed by the acid into water and carbon monoxide, with the resulting water reducing the catalyst activity, and the carbon monoxide being discharged as a gas to cause in undesired circumstantial problems; (3) since the excess formic acid can not be recovered, it results in disadvantages in view of the cost; and (4) since formic acid is often less miscible with olefins and alcohols, it requires to introduce the formic acid and the reaction substrate at an accurate dropping rate to the reaction system for preventing the decrease in the yield, which renders the procedures much complicated.
Further, one of the problems involved throughout the Koch reactions is that acid has to be used in an extremely large amount. Since the acid can not be always recovered depending on the case, the disposition for the great amount of wasted acid provides a significant problem in view of the production step. Even if the acid can be recovered, the use of such great amount of acid inevitably leads to the disadvantage of decreasing the charge amount per one reaction cycle.